when we write a post in wp, there is a thing called custom fields.. is that of any use with seo?? or is it simply some extra info? can anyone help me out with this?
From what I know the custom fields would be used by plugin authors and called using PHP -- they won't just be added to your displayed html code (a plugin would have to grab the data and use it). (Mind you, that's not my expertise!). If you use something like All-In-One SEO it'll have its own fields for keywords and description... so you don't need to have custom fields perform that kind of function.
This is explained with ease on wordpress site itself. http://codex.wordpress.org/Using_Custom_Fields Code (markup):